An internal combustion engine of a vehicle can be generally classified into a gasoline engine and a diesel engine.
In the gasoline engine, which uses gasoline as a fuel, air and the gasoline fuel are mixed and compressed inside a cylinder to achieve combustion.
In the diesel engine, which uses diesel as a fuel, air enters a cylinder by a piston and compressed by high pressure, and thereafter, the fuel is injected at a high temperature and a high pressure to achieve combustion through self-ignition.
The diesel engine has higher thermal efficiency than the gasoline engine and lower fuel consumption. Further the fuel for the diesel engine is inexpensive, operation cost is economical, and a usage range of the diesel fuel is wide, and as a result, there is flexibility in using alternative fuel.
Recently, a diesel hybrid vehicle having the diesel engine and an electric motor as driving sources has been developed.
Since a great quantity of impurities and moisture are included in the diesel engine, a filtering process of removing the impurities and the moisture is required before supplying the fuel to the diesel engine in which a fuel filter is mounted and used for filtering.
When the moisture is introduced into the diesel engine, flow of the fuel is interfered due to cold weather in the wintertime, which causes a start failure or an idle failure and further causes discharged gas not to satisfy a discharged gas regulation value.
In the diesel engine, the fuel lubricates fuel associated parts, such as a high-pressure pump, a common rail, an injector, and the like, and when the moisture is introduced into such fuel associated parts and the fuel filter, damages and corrosion occur in the diesel engine.
Accordingly, the fuel filter includes a filtering element for removing the impurities and a moisture separator for separating the moisture, which is included in the fuel, and for storing the separated moisture in a fuel tank.
The fuel tank of the moisture separator stores water in which the moisture which is collected and stagnates and includes a water sensor for sensing the water.
The water sensor has a switch in which (+) and (−) terminals contact with each other when a water level in the fuel tank reaches a predetermined amount. When the water sensor is turned on as the terminals contact with each other, a warning lamp in a cluster is turned on to notify the water level to a driver.
Therefore, the driver recognizes the rise in the water level through the warning lamp to remove the water in the moisture separator.
The diesel engine is controlled by a failure diagnosis logic that diagnoses a failure of the water sensor to turn on the warning lamp to notify the driver when the failure occurs.
When the failure is sensed in the water sensor, the driver is notified by limiting an engine torque.
FIG. 1 is a flowchart illustrating a process of performing a water sensor failure diagnosis and an engine torque limit in a related art. FIG. 2 is a block diagram illustrating a water sensor 10, an engine control unit (ECU) 20, and a cluster controller 30.
Referring to FIGS. 1 and 2, when a failure occurs in the water sensor 10 mounted on a fuel filter (S1), the ECU 20 receives a signal transmitted from the water sensor 10 to recognize the failure of the water sensor 10 through a failure diagnosis logic (S2).
The water sensor 10 directly transfers a failure state to the cluster controller 30, and the cluster controller 30 exhibits a warning label through a display device 32 while turning on a warning lamp 31 in a cluster to notify a driver the failure (S3).
Subsequently, the ECU 20 performs a torque limitation to forcibly induce the driver to check a vehicle (S4).
The fuel filter and the water sensor 10, and the failure diagnosis of the water sensor 10 and the torque limitation during the failure are applied to the diesel hybrid vehicle. FIG. 3 is a diagram for describing a driving mode of a diesel hybrid vehicle.
In a diesel hybrid vehicle, a driving mode is determined by a hybrid control unit (HCU) according to a driving condition and an engine driving mode in which an engine runs and a hybrid driving mode in which the engine is turned off are repeated several times in one driving cycle.
When the diesel hybrid vehicle enters the hybrid driving mode while the engine is running, the engine stops (engine is turned off). Although the engine is turned off in the hybrid driving mode, the vehicle is on, and thus, the sensing operation of the water sensor 10 and the operation of the warning lamp 31 can be performed, and the failure of the water sensor 10 can be diagnosed.
When the ECU 20 recognizes the failure of the water sensor 10 in the hybrid driving mode, the ECU 20 immediately limits the torque while the engine is running in which the hybrid driving mode is changed to the engine driving mode by the HCU according to the driving condition while the hybrid driving mode is maintained.
When the failure occurs in the water sensor during the engine driving mode in which the engine runs, the engine torque limitation is immediately performed.
According to the related art, when the failure occurs in the water sensor in the hybrid driving mode, the engine torque limitation is immediately performed when the engine driving mode starts while there is no torque limitation during the hybrid driving mode. Thus, the forcible failure situation transferring method may cause driver's dissatisfaction with a vehicle system.
When the torque limitation to reduce the engine torque is achieved while the driver does not recognize the failure situation through the warning lamp and the warning label after the failure occurs in the water sensor, the driver may not feel safe and vehicle drivability and merchantability decrease.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.